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Biomedical subjects

R Moore

Publications and source records attributed to R Moore.

At least 271 records · Page 15Linked to original sources
PubMed1990

Comparative effectiveness of a clinostat and a slow-turning lateral vessel at mimicking the ultrastructural effects of microgravity in plant cells.

The object of this research was to determine how effectively the actions of a clinostat and a fluid-filled, slow-turning lateral vessel (STLV) mimic the ultrastructural effects of microgravity in plant cells. We accomplished this by qualitatively and quantitatively comparing the ultrastructures of cells grown on clinostats and in an STLV with those of cells grown at 1 g and in microgravity aboard the Space Shuttle Columbia. Columella cells of Brassica perviridis seedlings grown in microgravity and in an STLV have similar structures. Both contain significantly more lipid bodies, less starch, and fewer dictyosomes than columella cells of seedlings grown at 1 g. Cells of seedlings grown on clinostats have significantly different ultrastructures from those grown in microgravity or in an STLV, indicating that clinostats do not mimic microgravity at the ultrastructural level. The similar structures of columella cells of seedlings grown in an STLV and in microgravity suggest that an STLV effectively mimics microgravity at the ultrastructural level.

Brassica↗
PubMed1990

Inducing gravitropic curvature of primary roots of Zea mays cv Ageotropic.

Primary roots of the mutant 'Ageotropic' cultivar of Zea mays are nonresponsive to gravity. Their root caps secrete little or no mucilage and touch the root only at the extreme apex. A gap separates the cap and root at the periphery of the cap. Applying mucilage from normal roots or substances with a consistency similar to that of mucilage to tips of mutant roots causes these roots to become strongly graviresponsive. Gravicurvature stops when these substances are removed. Caps of some mutants secrete small amounts of mucilage and are graviresponsive. These results indicate that (a) the lack of graviresponsiveness in the mutant results from disrupting the transport pathway between the cap and root, (b) movement of the growth-modifying signal from the cap to the root occurs via an apoplastic pathway, and (c) mucilage is necessary for normal communication between the root cap and root in Zea mays cv Ageotropic.

Agar↗
PubMed1990

Modulation of fluid absorption and the secretory response of rat jejunum to cholera toxin by dietary fat.

To study the effects of dietary fat on jejunal water and ion absorption and on cholera toxin-induced secretion, 3 week old Sprague Dawley rats were fed isocaloric diets. Forty per cent of the total calories were given as fat, as butter (high saturated fat), olive oil (high monounsaturated fat), or corn oil (high polyunsaturated fat), with one group on low fat (10% of calories) standard laboratory diet as controls. During in vivo jejunal perfusion studies we found that (i) a polyunsaturated fat (corn oil) supplemented diet improves jejunal absorption of water and electrolytes and these changes are independent of the observed concentrations of luminal prostaglandins; (ii) high dietary fat appreciably reduced the secretory response to cholera toxin, probably without fundamentally changing the mechanism by which cholera toxin induces secretion. We conclude that dietary fat composition altered the permeability and transport characteristics of the small intestine. This observation might have relevance to some human diarrhoeal disorders.

Animals↗
PubMed1990

C. difficile toxin A increases intestinal permeability and induces Cl- secretion.

Mucosal sheets of guinea pig ileum mounted in Ussing chambers were used to determine effects of highly purified Clostridium difficile toxin A on intestinal structure and barrier function in the absence of recruited neutrophils and blood flow. With the use of standard electrophysiological and morphological techniques, our results indicate that 5 micrograms/ml mucosal toxin A induces substantial alteration in epithelial permeability and in structure of absorptive cells. Transepithelial fluxes of mannitol (3.6 A) and inulin (11.5 A) increased 20-80 min after toxin A exposure (63 +/- 13 vs. 149 +/- 14 and 2.33 +/- 0.43 vs. 7.03 +/- 1.0 nmol.cm-2.h-1 for mannitol and inulin; controls vs. toxin exposed, respectively, both P less than 0.01). Toxin A exposure diminished short-circuit current (153 +/- 8 vs. 77 +/- 6 microA/cm2 for control and toxin exposed, respectively, P less than 0.001), decreased transepithelial electrical resistance (61.6 +/- 3 vs. 50.1 +/- 3.9 omega.cm2 for control and toxin exposed, respectively, P less than 0.05), increased passive permeation of Na+ (19.1 +/- 0.9 vs. 27.4 +/- 0.9 mumol.cm-2.h-1 for control and toxin exposed, respectively), and induced a Cl- secretory response (net flux 3.65 +/- 3.0 vs. -4.62 +/- 2.6 mumol.cm-2.h-1, for control and toxin exposed, respectively, P less than 0.05) over the 2-h experimental time course. Toxin A-induced structural alterations of villus tip absorptive cells were strikingly similar to those induced by the actin-binding agent cytochalasin D. Specifically, cells displayed constricted subjunctional zones, flared microvillus brush borders, condensation of microfilaments in the zone of the perijunctional actomyosin ring, and breakdown of intercellular tight junctions.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Redistribution of regional and organ blood volume and effect on cardiac function in relation to upright exercise intensity in healthy human subjects.

To determine the effect of relative exercise intensity on organ blood volume and its relation to cardiac function, changes in relative blood volume and cardiac function were monitored with radionuclide techniques in 14 healthy volunteers. After labeling the subject's red cells with technetium 99m, we acquired data at rest, zero-load cycling, and at 50%, 75%, and 100% of maximal oxygen uptake. From rest to zero-load cycling, leg blood volume decreased 32 +/- 2% (mean +/- SEM), whereas relative end-diastolic blood volume increased 9.6 +/- 1.2%, and lung blood volume increased 18 +/- 2%, suggesting that the lungs may act as a blood volume buffer during periods of acutely increased venous return. With relative increasing exercise, leg blood volume stabilized, and then the blood volume in the abdominal organs decreased, further augmenting cardiopulmonary blood volume; leg blood volume and abdominal blood volume decreased by 23 +/- 2% and 19 +/- 2% from baseline, respectively, whereas thoracic blood volume increased 38 +/- 4%. In the abdomen, large decreases in blood volume were observed in the spleen (46 +/- 2%), kidney (24 +/- 4%), and liver (18 +/- 4%). In contrast, lung blood volume increased 50 +/- 4%, with the upper lung fields increasing more than the lower. Blood sampling revealed an increase in the hematocrit level by 4.3 +/- 0.4 units at peak exercise that paralleled the decrease in splenic blood volume (r2 = -0.64, p less than 0.001), suggesting a role for the spleen in augmenting cardiovascular performance by the release of concentrated red blood cells into general circulation. We conclude that upright exercise results in marked blood volume shifts from the legs and abdominal organs to the heart and lungs in a dynamic process correlating closely with oxygen consumption.

Adult↗
PubMed1990

Influence of electrical fields and asymmetric application of mucilage on curvature of primary roots of Zea mays.

Primary roots of Zea mays cv. Yellow Dent growing in an electric field curve towards the anode. Roots treated with EDTA and growing in electric field do not curve. When root cap mucilage is applied asymmetrically to tips of vertically-oriented roots, the roots curve toward the mucilage. Roots treated with EDTA curve toward the side receiving mucilage and toward blocks containing 10 mM CaCl2, but not toward "empty" agar blocks or the cut surfaces of severed root tips. These results suggest that 1) free calcium (Ca) is necessary for root electrotropism, 2) mucilage contains effector(s) that induce gravitropiclike curvature, and 3) mucilage can replace gravitropic effectors chelated by EDTA. These results are consistent with the hypothesis that the downward movement of gravitropic effectors to the lower sides of tips of horizontally-oriented roots occurs at least partially in the apoplast.

Biological Transport↗
PubMed1990

Morphometric analysis of epidermal differentiation in primary roots of Zea mays.

Epidermal differentiation in primary roots of Zea mays was divided into six cell types based on cellular shape and cytoplasmic appearance. These six cell types are: 1) apical protoderm, located at the tip of the root pole and characterized by periclinally flattened cells; 2) cuboidal protoderm, located approximately 230 microns from the root pole and characterized by cuboidal cells; 3) tabular epidermis, located approximately 450 microns from the root pole and characterized by anticlinally flattened cells; 4) cuboidal epidermis, located approximately 900 microns from the root pole and characterized by cuboidal cells having numerous small vacuoles; 5) vacuolate cuboidal epidermis, located approximately 1,500 microns from the root pole and characterized by cuboidal cells containing several large vacuoles; and 6) columnar epidermis, located approximately 2,200 microns from the root pole (i.e., at the beginning of the zone of elongation) and characterized by elongated cells. We also used stereology to quantify the cellular changes associated with epidermal differentiation. The quiescent center and the apical protoderm have significantly different ultrastructures. The relative volume of dictyosomes increases dramatically during the early stages of epidermal differentiation. This increase correlates inversely with the amount of coverage provided by the root cap and mucilage.

Cell Compartmentation↗
PubMed1990

Microsurgical removal of epidermal and cortical cells: evidence that the gravitropic signal moves through the outer cell layers in primary roots of maize.

There is general agreement that during root gravitropism some sort of growth-modifying signal moves from the cap to the elongation zone and that this signal ultimately induces the curvature that leads to reorientation of the root. However, there is disagreement regarding both the nature of the signal and the pathway of its movement from the root cap to the elongation zone. We examined the pathway of movement by testing gravitropism in primary roots of maize (Zea mays L.) from which narrow (0.5 mm) rings of epidermal and cortical tissue were surgically removed from various positions within the elongation zone. When roots were girdled in the apical part of the elongation zone gravitropic curvature occurred apical to the girdle but not basal to the girdle. Filling the girdle with agar allowed curvature basal to the girdle to occur. Shallow girdles, in which only two or three cell layers (epidermis plus one or two cortical cell layers) were removed, prevented or greatly delayed gravitropic curvature basal to the girdle. The results indicate that the gravitropic signal moves basipetally through the outermost cell layers, perhaps through the epidermis itself.

Agar↗
PubMed1990

Comparison of DNA:DNA homology and enzymatic activity between Pasteurella haemolytica and related species.

A commercially available microbiological identification system and DNA:DNA hybridization were used to determine relationships between and within serovars 1-13 of Pasteurella haemolytica, and between P haemolytica and P multocida and 4 species of Actinobacillus. All serovars of P haemolytica that belonged to biovar A were related with mean DNA homology of 78%, whereas all serovars of P haemolytica that belonged to biovar T were related to each other with mean DNA homology of 90%. The DNA:DNA hybridization between strains of biovars A and T ranged from 3 to 13%, indicating little or no genetic relationship between the 2 biovars of P haemolytica. The DNA homology between all serovars of P haemolytica and other species of non-P haemolytica bacteria tested (P multocida and actinobacilli) was less than 14%, suggestive of essentially no genetic relationship of P haemolytica with the ATCC reference strains of the genus Pasteurella or the genus Actinobacillus. Enzymatic differences were observed between P haemolytica and the other non-P haemolytica bacteria tested; however, the microbiological identification system that uses enzymatic reactions could not distinguish among biovars of P haemolytica. Results of this research support other data that suggest that biovars A and T of P haemolytica should be classified as separate species, but do not support the inclusion of either biovar A or T within the genus Actinobacillus.

Acid Phosphatase↗
PubMed1990

[Phenomenon of dental fear].

Odontophobia is a rather unique phobia with special psychosomatic components that impact on the dental health of odontophobic persons. It also has psychosocial components largely as a result of destruction of the teeth and subsequent embarrassment that can affect a person and cause a vicious cycle of dental fear. The phenomenon is facilitated by misunderstandings and myths generated by both patients and dentists. The most common reasons given in the literature for such strong fears of dental treatment are: 1) bad experiences in childhood for 85% of cases, 2) feeling of powerlessness and lack of control over personal emotional reactions and over the social situation in the dental chair, 3) social learning processes in which the image of the dentist is cast in a negative light by the mass media or by the person's relatives or friends and 4) that the person has other psychologic problems (in 20% of cases), such as serious phobias and/or neuroses. A strategy of researching and thus tackling the problem is presented which focuses on three essential targets that require studying and change: 1) the community at large and their image of the dentist, 2) the patient role and 3) the dentist role. Various model projects are presented along with their diagnostic systems. These are seen to focus in varying degrees on different elements of the target groups that effect the dentist-patient relationship but the need to come out into the community and make the social environment right for these patients is an important factor in all strategies.(ABSTRACT TRUNCATED AT 250 WORDS)

Communication↗
PubMed1990

[How to evaluate dental fear].

The measurement of complex behavioral phenomena like dental fear requires allegiance to two great domains that often seem to conflict with one another: natural scientific method and the seemingly unpredictable human psyche. The need to preserve strict objectivity in scientific observations and yet flexibility enough to appreciate the contextual facets of psychological and social variables are a difficult combination. There are differing scientific philosophies that are presented here not as incompatible opposites, but as a complementary team of approaches to aid human behavioral problem solving in dental clinical science. The "positivistic falsification" tradition requires "objective" double-blind type experimental hypothesis testing, while the "phenomenologic-hermaneutic" tradition requires the researcher to grasp the context of the phenomena to be studied in order to understand and thereafter test the most relevant variables. Thus, there is a need for both traditions, since the relevant variables should be systematically evaluated (qualitative phase) before they can be adequately tested (quantitative phase). Clinical evaluation of dental fear draws on information gathered about a patient's verbal (cognitive) descriptions, behavioral symptoms and physiologic reactions. Commonly used psychometric testing scales developed to differentiate fears specific to dentistry, as opposed to general anxiety syndromes, are the result of observations made in several qualitative studies that not all dental phobics have general anxiety symptoms. Examples of these and other tests are listed and described, noting that verbal and behavioral testing appear more reliable than physiologic indicators. The patient's subjective sense of improvement is deemed to be an important factor in their confidence and efficacy to deal with the threats that the dental environment can bring them.(ABSTRACT TRUNCATED AT 250 WORDS)

Dental Care↗
PubMed1990

[Dental fear--relevant clinical methods of treatment].

The treatment of odontophobia is often relegated to treatment under general anesthesia as a quick solution, but this has proven to be ineffective in the long run. Other more cognitive approaches include flooding, where the patient learns through courageous participation to endure the fear through several routine dental treatments. Since this can often backfire on the patient, systematic desensitization is preferred, in combination with psychotherapy that is aided by progressive muscle relaxation or fading, biofeedback training or stress inoculation training. Hypnosis can also help the patient to restructure negative thinking towards more positive expectations from treatment. These are all meant to build up the patient's psychic coping resources. Assertiveness training in psychotherapy is used to build up the patient's social skills so that he/she can deal with dental personal in a diplomatic yet self determined way. Finally, modelling good patient behaviors to dental fear patients has been shown to be effective and is especially used by childrens' dentists. Use of sedatives the night before a dental appointment is often helpful and enables some patients with insomnia to be fresh and rested in order to deal with the often strenuous learning processes described above.

Dental Care↗
PubMed1990

Structure and function of the intestinal epithelial barrier in health and disease.

The major and rate-limiting barrier to transepithelial permeation in the intestine is the intercellular tight junction. Tight junction structure is often cell type specific and general but imperfect correlates between tight junction structure and permeability exist. The structure and permeability of this key barrier is not static and can be regulated physiologically. The means of regulation appears to involve the cytoskeleton of neighboring epithelial cells (particularly absorptive cells). Meal-related solutes--nutrients such as glucose--can reversibly enhance the permeability of absorptive cell tight junctions. Although this may substantially enhance the ability of the small intestine to harvest meal-related nutrients, it is conceivable that this may also result in transient exposure of the subepithelial compartment to potentially noxious lumenal compounds. Some features found in many intestinal disease states such as PMN migration across the epithelium may also result in transient barrier defects. With PMN transmigration it is clear that even macromolecules may permeate junctions being impaled by PMNs. When disease processes finally result in focal epithelial denudation, the epithelium has the potential of resealing such defects with remarkable efficiency. The preceding discussion highlights how dynamic the tight junction is and sets the stage for future work aimed at understanding the initial signaling events and intracellular cascade(s) that allow this major barrier to demonstrate such plasticity.

Epithelial Cells↗
PubMed1989

Genetic structure, function and regulation of the transposable element IS21.

The IncP plasmid R68.45 and other plasmids carrying tandem repeats of the insertion sequence IS21 [= (IS21)2] produce replicon fusions via transposition at high frequencies in Escherichia coli and other gram-negative bacteria, whereas plasmids with a single IS21 copy, e.g. R68, give replicon fusions rarely. The 2131 bp nucleotide sequence of IS21 was determined; at the ends there were 11 bp inverted repeats with one mismatch. Two adjacent open reading frames, istA and istB, were located on one DNA strand of IS21. In E. coli maxicells, polypeptides of 46 kDa (the istA gene product) and 30 kDa (the istB gene product) were expressed by (IS21)2 plasmids, but not by IS21 plasmids. Genetic analysis of (IS21)2 plasmids indicates that the IS21-IS21 junctions form a promoter, which initiates transcription of the istAB operon in one of the two IS21 elements. A single IS21 element fused to an inducible external tac promoter expressed both proteins after induction, but did not promote effective replicon fusion, unless an IS21-IS21 junction (the preferred site for IS21 transposase action) was also present on the plasmid carrying the tac-IS21 construct. The sequences located between the IS21 elements in (IS21)2, 3 bp in R68.45 or 2 bp in pME28, were not recovered in the replicon fusion products. Homologous recombination between the directly oriented IS21 elements in the fusion products led to plasmids with a single IS21 insertion. Analysis of the latter showed that IS21 had a low, but not totally random specificity of insertion and created target duplications of 4 bp (occasionally 5 bp).(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1989

Responses to ozone of insects feeding on a crop and a weed species.

The influence of ozone on insect herbivore growth and population development was investigated. Fumigation of both pea (Pisum sativum L.) and dock (Rumex obtusifolius L.) at a range of O(3) concentrations between 21-206 nl litre(-1) produced changes in mean relative growth rates of the aphids Acyrthosiphon pisum Harris and Aphis rumicis L. of between 24 and -6% relative to controls. However, there was no evidence of a dose-related response to O(3) fumigation and no clear differences in aphid response when fumigated with the plant on prefumigated or previously unfumigated plant material. It is suggested that this may, in part, be due to the presence of NO contamination during O(3) fumigation. However, the MRGR of dock aphids was found to be greater on new compared to old leaves as well as the increase on the new growth and decrease on the old growth of fumigated plants relative to unfumigated controls. The size of egg batches of the chrysomelid beetle Gastrophysa viridula Degeer were found to be larger, survival and productivity of larvae was higher, and the food consumption lower on R. obtusifolius fumigated with 70 nl litre(-1) O(3) compared with unfumigated controls. This meant that these beetle larvae consumed less leaf area per mg of production on fumigated leaves probably because of their better nutritional quality and/or reduced leaf defences. However, the rate of development of larvae was similar on fumigated and control plants.

Journal Article↗